Lens unit and manufacturing method therefor

Abstract

A lens unit may include at least four lens groups and a tube-shaped holder holding the lens groups. The tube-shaped holder is provided with a second lens group holding part provided with a protruded part surrounding an outer peripheral end part of the second lens group through a gap space and the protruded part is provided with a caulked part which is deformed so as to cover the outer peripheral end part from the object side. The protruded part may be provided with a thick portion and a thin portion extended to the front side from the thick portion and the thin portion is caulked by being plastically deformed to be the caulked part. After the second lens group is mounted on an inner side to the protruded part, the position of the second lens group is adjusted and then a caulked part is formed.

What is claimed is: 
     
       1. A lens unit for use with an object to be photographed, comprising:
 a first lens group; 
 a second lens group 
 a third lens group; 
 a fourth lens group; and 
 a tube-shaped holder which holds the first lens group, the second lens group, the third lens group, the and fourth lens group; 
 wherein the first lens group, the second lens group, the third lens group, and the fourth lens group are arranged in sequential order from an object side closest to the object to be photographed; 
 wherein the tube-shaped holder is provided with a second lens group holding part which holds a second lens group located at a second position from the object side; 
 wherein the second lens group holding part is provided with a protruded part which surrounds an outer peripheral end part of the second lens group through a gap space between the outer peripheral end part of the second lens group and the protruded part in a first direction intersecting an optical axis direction and in a second direction intersecting the optical axis direction and the first direction; and 
 wherein the protruded part is provided with a caulked part which is deformed so as to cover the outer peripheral end part from the object side. 
 
     
     
       2. The lens unit according to  claim 1 , wherein the protruded part is provided at plural positions in a circumferential direction. 
     
     
       3. The lens unit according to  claim 1 , wherein the second lens group holding part and the second lens group are fixed to each other with an adhesive. 
     
     
       4. The lens unit according to  claim 3 , wherein the lens groups located at a third or succeeding position from the object side comprises a cemented lens constituted of glass lenses and a cemented lens constituted of plastic lenses. 
     
     
       5. The lens unit according to  claim 4 , wherein a viewing angle is 170° or more. 
     
     
       6. The lens unit according to  claim 1 , wherein
 the tube-shaped holder is provided with a bottom plate part located at the most rear side in the optical axis direction, a tube-shaped body part extended from an outer circumferential end of the bottom plate part to a front side which is the object side, a ring-shaped flange part which is enlarged from the tube-shaped body part to an outer side in a radial direction, and a large diameter tube part which is provided with a larger diameter than the tube-shaped body part and is extended to the front side from the flange part, and 
 the protruded part of the second lens group holding part is formed so as to protrude to the front side from an inner side of the flange part. 
 
     
     
       7. The lens unit according to  claim 6 , wherein
 the tube-shaped holder holds, in order from an object side, a first lens group having negative power, the second lens group having negative power, a third lens group having positive power, and a fourth lens group having positive power, 
 the first lens group is positioned and fixed to the large diameter tube part, and 
 the third lens group and the fourth lens group are positioned and held by the tube-shaped body part. 
 
     
     
       8. The lens unit according to  claim 6 , wherein
 the protruded part is provided with a thick portion protruded to the front side from the flange part and a thin portion extended to the front side from the thick portion, 
 an inner face of the thick portion and an inner face of the thin portion form a continuous surface and are formed to be concentric shape with the outer peripheral end part of the second lens group, and 
 the thin portion is caulked to be the caulked part. 
 
     
     
       9. The lens unit according to  claim 8 , wherein the caulked part is formed to be plastically deformed so as to cover the outer peripheral end part of the second lens group on the front side by heating and melting the thin portion of the protruded part. 
     
     
       10. A manufacturing method for a lens unit including at least four lens groups and a tube-shaped holder holding the lens groups, comprising:
 previously providing in the tube-shaped holder with a second lens group holding part for holding a second lens group located at a second position from an object side; 
 previously providing in the second lens group holding part with a protruded part for surrounding an outer peripheral end part of the second lens group through a gap space between the outer peripheral end part and the protruded part in a first direction intersecting an optical axis direction and in a second direction intersecting the optical axis direction and the first direction; 
 mounting the second lens group on an inner side with respect to the protruded part; 
 after mounting the second lens group, adjusting position of the second lens group in the first direction and the second direction, and 
 after adjusting the position, forming a caulked part which covers the outer peripheral end part on the object side by plastically deforming the protruded part. 
 
     
     
       11. The manufacturing method for a lens unit according to  claim 10 , further comprising fixing the second lens group to the second lens group holding part with an adhesive after forming the caulked part. 
     
     
       12. The manufacturing method for a lens unit according to  claim 10 , wherein the lens groups located at a third or succeeding position from the object side comprises a cemented lens constituted of glass lenses and a cemented lens constituted of plastic lenses. 
     
     
       13. The manufacturing method for a lens unit according to  claim 10 , wherein a viewing angle is 170° or more. 
     
     
       14. The manufacturing method for a lens unit according to  claim 10 , wherein the protruded part is provided at plural positions in a circumferential direction. 
     
     
       15. The manufacturing method for a lens unit according to  claim 10 , wherein
 the tube-shaped holder is provided with a bottom plate part located at the most rear side in the optical axis direction, a tube-shaped body part extended from an outer circumferential end of the bottom plate part to a front side which is the object side, a ring-shaped flange part which is enlarged from the tube-shaped body part to an outer side in a radial direction, and a large diameter tube part which is provided with a larger diameter than the tube-shaped body part and is extended to the front side from the flange part, and 
 the protruded part of the second lens group holding part is formed so as to protrude to the front side from an inner side of the flange part. 
 
     
     
       16. The manufacturing method for a lens unit according to  claim 15 , wherein
 the protruded part is provided with a thick portion protruded to the front side from the flange part and a thin portion extended to the front side from the thick portion, 
 an inner face of the thick portion and an inner face of the thin portion form a continuous surface and are formed to be concentric shape with the outer peripheral end part of the second lens group, and 
 the thin portion is caulked to be the caulked part. 
 
     
     
       17. The manufacturing method for a lens unit according to  claim 16 , wherein the caulked part is formed to be plastically deformed so as to cover the outer peripheral end part of the second lens group on the front side by heating and melting the thin portion of the protruded part. 
     
     
       18. A manufacturing method for a lens unit including at least four lens groups and a tube-shaped holder holding the lens groups, comprising:
 previously providing in the tube-shaped holder with a second lens group holding part for holding a second lens group located at a second position from an object side; 
 previously providing in the second lens group holding part with a protruded part for surrounding an outer peripheral end part of the second lens group through a gap space between the outer peripheral end part and the protruded part in a first direction intersecting an optical axis direction and in a second direction intersecting the optical axis direction and the first direction; 
 mounting the second lens group on an inner side with respect to the protruded part; 
 after mounting the second lens group, forming a caulked part which covers the outer peripheral end part on the object side by plastically deforming the protruded part so that the second lens group is capable of being adjusted on the inner side of the protruded part; 
 after forming the caulked part, adjusting position of the second lens group in the first direction and the second direction. 
 
     
     
       19. The manufacturing method for a lens unit according to  claim 18 , further comprising fixing the second lens group to the second lens group holding part with an adhesive after adjusting the position of the second lens group. 
     
     
       20. The manufacturing method for a lens unit according to  claim 18 , wherein the lens groups located at a third or succeeding position from the object side comprises a cemented lens constituted of glass lenses and a cemented lens constituted of plastic lenses. 
     
     
       21. The manufacturing method for a lens unit according to  claim 18 , wherein a viewing angle is 170° or more. 
     
     
       22. The manufacturing method for a lens unit according to  claim 18 , wherein the protruded part is provided at plural positions in a circumferential direction. 
     
     
       23. The manufacturing method for a lens unit according to  claim 18 , wherein
 the tube-shaped holder is provided with a bottom plate part located at the most rear side in the optical axis direction, a tube-shaped body part extended from an outer circumferential end of the bottom plate part to a front side which is the object side, a ring-shaped flange part which is enlarged from the tube-shaped body part to an outer side in a radial direction, and a large diameter tube part which is provided with a larger diameter than the tube-shaped body part and is extended to the front side from the flange part, and 
 the protruded part of the second lens group holding part is formed so as to protrude to the front side from an inner side of the flange part. 
 
     
     
       24. The manufacturing method for a lens unit according to  claim 23 , wherein
 the protruded part is provided with a thick portion protruded to the front side from the flange part and a thin portion extended to the front side from the thick portion, 
 an inner face of the thick portion and an inner face of the thin portion form a continuous surface and are formed to be concentric shape with the outer peripheral end part of the second lens group, and 
 the thin portion is caulked to be the caulked part.